A semiconductor integrated circuit chip is typically fabricated with a back-end-of-line (BEOL) interconnect structure, which comprises multiple levels of metal wiring and inter-level metal vias, to connect various integrated circuit components and devices that are fabricated as part of a front-end-of-line (FEOL) layer of the semiconductor integrated circuit chip. Current state of the art BEOL process technologies typically implement copper to form BEOL interconnects, as the use of copper interconnects, as compared to conventional aluminum interconnects, are known to significantly reduce resistance in the BEOL interconnect structure, resulting in improved conduction and higher performance. As copper interconnect structures are scaled down, however, current density in the copper interconnect structures increases exponentially, resulting in current-driven electromigration of copper atoms. In the context of copper interconnect structures, electromigration is the transport of the copper material caused by the gradual movement of ions in the copper interconnect structures due to momentum transfer between conducting electrons and diffusing copper atoms. When copper interconnect structures undergo electromigration, the copper atoms can diffuse away from the copper interconnect structures and into other regions of the integrated circuit, thereby leading to various defects in the copper interconnect structure and in the other regions to which copper atoms diffuse.
A barrier metal is a material used in integrated circuits to chemically isolate semiconductor material from soft metal interconnect material, while maintaining an electrical connection between the two materials. For instance, in the BEOL interconnect structure described above, a layer of barrier metal typically surrounds each copper interconnect. This prevents diffusion of copper into the surrounding semiconductor material. As such, a barrier metal is typically comprised of a material that is inert so as to mitigate soft metal (e.g., copper) contamination while being conductive enough to allow the flow of electricity from the interconnect to other surrounding regions. However, typical barrier metals (e.g., chromium (Cr), tantalum (Ta), titanium (Ti), tungsten (W), etc.) do not adhere well to the surrounding regions of the interconnect structure such as dielectric materials.